// 
// Copyright (c) 2004-2006 Jaroslaw Kowalski <jaak@jkowalski.net>
// 
// All rights reserved.
// 
// Redistribution and use in source and binary forms, with or without 
// modification, are permitted provided that the following conditions 
// are met:
// 
// * Redistributions of source code must retain the above copyright notice, 
//   this list of conditions and the following disclaimer. 
// 
// * Redistributions in binary form must reproduce the above copyright notice,
//   this list of conditions and the following disclaimer in the documentation
//   and/or other materials provided with the distribution. 
// 
// * Neither the name of Jaroslaw Kowalski nor the names of its 
//   contributors may be used to endorse or promote products derived from this
//   software without specific prior written permission. 
// 
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
// AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 
// IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 
// ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE 
// LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR 
// CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
// SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS 
// INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN 
// CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 
// ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF 
// THE POSSIBILITY OF SUCH DAMAGE.
// 

using System;
using System.Text;
using System.IO;
using NLog.Internal;
using System.ComponentModel;
using NLog.Config;

namespace NLog.LayoutRenderers
{
    /// <summary>
    /// Contents of the specified file.
    /// </summary>
    [LayoutRenderer("file-contents")]
    public class FileContentsLayoutRenderer: LayoutRenderer
    {
        private Layout _fileName;
        private System.Text.Encoding _encoding = System.Text.Encoding.Default;
        private string _lastFileName = "";
        private string _fileContents;

        /// <summary>
        /// Returns the estimated number of characters that are needed to
        /// hold the rendered value for the specified logging event.
        /// </summary>
        /// <param name="logEvent">Logging event information.</param>
        /// <returns>The number of characters.</returns>
        /// <remarks>
        /// If the exact number is not known or
        /// expensive to calculate this function should return a rough estimate
        /// that's big enough in most cases, but not too big, in order to conserve memory.
        /// </remarks>
        protected internal override int GetEstimatedBufferSize(LogEventInfo logEvent)
        {
            return 8;
        }

        /// <summary>
        /// Name of the file.
        /// </summary>
        [DefaultParameter]
        public Layout FileName
        {
            get { return _fileName; }
            set { _fileName = value; }
        }

        /// <summary>
        /// File encoding.
        /// </summary>
        /// <value>The encoding.</value>
        public string Encoding
        {
            get { return _encoding.WebName; }
            set { _encoding = System.Text.Encoding.GetEncoding(value); }
        }

        /// <summary>
        /// Renders the contents of the specified file and appends it to the specified <see cref="StringBuilder" />.
        /// </summary>
        /// <param name="builder">The <see cref="StringBuilder"/> to append the rendered data to.</param>
        /// <param name="logEvent">Logging event.</param>
        protected internal override void Append(StringBuilder builder, LogEventInfo logEvent)
        {
            lock (this)
            {
                string fileName = _fileName.GetFormattedMessage(logEvent);

                if (fileName != _lastFileName)
                {
                    ReadFileContents(fileName);
                    _lastFileName = fileName;
                }
            }
            builder.Append(_fileContents);
        }

        private void ReadFileContents(string fileName)
        {
            _fileContents = "";

            try
            {
                using (StreamReader sr = new StreamReader(fileName, _encoding))
                {
                    _fileContents = sr.ReadToEnd();
                }
            }
            catch (Exception ex)
            {
                InternalLogger.Warn("Cannot read file {0}: {1}", FileName, ex);
            }
        }
    }
}
